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The consequences of earthquakes
History on earthquakes essay
The consequences of earthquakes
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I chose to research earthquakes and the prediction of earthquakes because I was curious as to how they work. In this paper, I will discus the history of earthquakes, the kinds and locations of earthquakes, earthquake effects, intensity scales, prediction, and my own predictions. An earthquake can be defined as vibrations produced in the earth's crust. Tectonic plates have friction between them which builds up as it tries to push away and suddenly ruptures and then rebounds. The vibrations can range from barely noticeable to a disastrous, and destructive act of nature. Six kinds of shock waves are generated in the process. Two are classified as body waves, that is, they travel through the inside of the earth and the other four are surface waves. The waves are further classified by the kinds of motions they incur to rock particles. Primary or compressional waves, known as P waves, send particles moving back and forth in the same direction as the waves are traveling, as secondary or transverse shear waves, known as S waves, create vibrations perpendicular to their direction of travel. P waves always travel at faster speeds than S waves, so whenever an earthquake occurs, P waves are the first to arrive and to be recorded at geophysical research stations worldwide. During ancient times very little was know about. Some of the ancient Greek philosophers connected earthquakes to underground winds, where others blamed them on fires in the depths of the earth. Around AD 130 the Chinese scholar Chang Heng, believing that waves must ripple through the earth from the source of an earthquake, created a bronze object to record the directions of such waves. Eight balls were carefully balanced in the mouths of eight dragons placed around the outside of the object. When a passing earthquake occurred the wave would cause one or more of the balls to drop. Earthquake waves were observed in this and other ways for centuries, but more scientific theories as to the causes of quakes were not proposed until modern times. One such concept was recreated and advanced in 1859 by an Irish engineer, Robert Mallet. Perhaps recalling on his knowledge of the strength and behavior of construction materials, Robert Mallet proposed that earthquakes occurred "either by sudden flexure and constraint of the elastic materials forming a portion of the earth's crust or by their giving way an... ... middle of paper ... ...orth of the earthquake that occurred the day before, this time I was wrong, there were two that occurred near the San Francisco bay area and none within a 50 mile radius of my approximation. The next couple days I predicted earthquakes that were within a 100 mile radius than were they actually occurred. From my experiments I concluded that predicting earthquakes was easy, you just have to pick a spot on the fault. The only thing that troubled me and probably most scientists, is magnitude, there is no possible way of predicting an earthquakes magnitude. Which is what we are really trying to predict. Earthquakes happen all the time, but what we are really trying to figure out how to predict is when a major earthquake is going to occur. I learned that earthquakes are almost unpredictable, and devastating acts of nature. I also learned how earthquakes occur and almost all of the "earthquake dictionary". There is still alot more to be known about earthquakes that we still do not know about today. Prediction of large earthquakes is still under development, where prediction of small, unnoticeable earthquakes can be easy to predict because they happen mainly around fault lines.
Earthquakes are a natural part of the Earth’s evolution. Scientific evidence leads many geologists to believe that all of the land on Earth was at one point in time connected. Because of plate tectonic movements or earthquakes, continental drift occurred separating the one massive piece of land in to the seven major continents today. Further evidence supports this theory, starting with the Mid-Atlantic ridge, a large mass of plate tectonics, which are increasing the size of the Atlantic Ocean while shrinking the Pacific. Some scientists believe that the major plate moveme...
Earthquakes play a major role into understanding the composition and materials that exist within the Earth (Merali and Skinner, 2009, p.252). Earthquakes are the main source of insight into the inner workings of the earth, due to the nature of the seismic waves they produce. P and S waves are reflected and refracted at different boundaries within the earth, and this enables seismologists to make inferences about the internal composition and structural of planet Earth. (Merali and Skinner, 2009, p.252).
Earthquakes in California are certainly not a surprise. What is a surprise is their unpredictability and randomness. Geologists say there is roughly a 50 percent chance that a magnitude 8 or more quake will hit the Los Angeles area sometime over the next 30 years. And, over the past twenty years, the Los Angeles area has witnessed several earthquakes, and in particular, two that were quite devastating; the 1971 San Fernando earthquake, and the January 17, 1994, Northridge Earthquake. Given the certainty that earthquakes will occur, they still seem to come as a surprise, and leave many communities unprepared to deal with their aftermath.
Ralph Waldo Emerson once said, “we learn geology the morning after the earthquake.” Fortunately for those living along the San Andreas Fault line in California, there are people behind the scenes, from geologists to city and emergency planners, who have no intention of waiting that long.
Heller, Arnie. "The 1906 San Francisco Earthquake." Science & Technology (2006): 4-12. Web. 8 May 2014.
In seismology, there are several types of waves studied, each of these waves have characteristics that define them. Seismic waves can be split into two categories, and they are body waves and surface waves. Body waves travel and move within the earths subsurface and inner layers. There are two types of body waves, P-Waves also known as compressional waves or primary waves, and S-Waves also called secondary or shear waves. The S-Waves have a vertical (Sv) and horizontal (Sh) component. “In an infinite homogenous isotropic medium, only P and S waves exist” (Telford et. al, 1990). On the other hand, as indicated by the name, surface waves travel and move along the surface of the earth. In general, surface waves have a lower frequency than body waves, therefore, they can easily be distinguished from body waves on a seismogram. There are two types of surface waves, Love waves and Rayleigh Waves. Love waves is the fastest surface wave, its movement mainly consists of a side to side completely horizontal motion. Rayleigh (1885) waves are surface waves that “roll” along the ground; they are a consequence of interfering P and Sv-Waves. Our project
Before examining the Northridge event, understanding the naturally occurring hazard that is an earthquake will help to better understand exactly what happened and why it was such an important geological event. With four distinct layers, two layers, the crust and upper portion of the mantle, compose the skin that is the surface layer of the Earth. The crust is not a single, continuous piece. It is actually several different pieces, or plates, that come together to form the puzzle that comprises the surface of the Earth. These plates are in constant motion rubbing against one another. These areas, known as fault lines, where the plates rub up against one another have spots where one plate ”gets stuck while the rest of the plate keeps moving. When the plate has moved far enough, the edges unstick and is how most of the earthquakes around the world occur” (Wald, 2012). The energy stored from the friction of the two plate...
What have they learned since the quake quite allot. The fault moved in a fashion that geologists of
After the Second World War seismometers were installed into the earth and showed that
The effects of the aftershocks were more emotional than physical which, given the seriousness and the consequences of the event, were natural and justified. Today, when Haiti struggles to eliminate the consequences of the quake and to restore the economic stability in the region, seismologists and scholars in geology science keep arguing about whether the Haiti earthquake could have been predicted. Whether seismologists could have predicted the Haiti earthquake is no longer important, and it is equally difficult to estimate the value and importance of the 2008 scientific report. Nevertheless, the Haiti earthquake teaches seismologists numerous lessons and once again emphasizes the need to develop sound technologies and systems, which would predict earthquakes and warn local populations about
Fig. 1 shows the map of a part of Asia in which the stars indicate the location of earthquakes and solid circle indicates the location of observing station Agra (27.2o N, 78o E). The details of these earthquakes are mentioned in table 1 which shows the days of occurrence, magnitudes, depths (km), locations (Latitude and Longitude in degrees), radius of influence zone (km) and distances from the Agra station (km). The radius of influence zone is calculated by using the expression R = 100.43M, where M is the magnitude of the earthquake [21]. Although these earthquakes have occurred far away from the observing station Agra, atleast two of them are well covered (> 1000 km) by the radius of the influence zone. The details of the earthquake data have been taken from United States Geological Survey (USGS) website www.earthquake.usgs.gov.in. We have also seen the variations of geomagnetic parameters such as Dst index and ∑ Kp index for each case separately and data have been taken from National Aeronautics and Space Administration (NASA) website http://omniweb.gsfc.nasa.gov/form/dx1.html. We can see from table 1 that all the earthquakes have shallow depths except one of them (46 km), but we cannot ignore this earthquake because of its relatively large magnitude (M = 7.8). Further, it may be seen from the table 1 that two of the earthquakes occurred in the month of April, one in July, and rest two in September, 2013.
Tillery, B. (2012). Wave Motions and Sound. Physical science (9th ed., pp. 115-134). New York,
Earthquakes belong to the class of most disastrous natural hazards. They result in unexpected and tremendous earth movements. These movements results from dissemination of an enormous amount of intense energy in form of seismic waves which are detected by use of seismograms. The impact of earthquakes leaves behind several landmarks including: destruction of property, extensive disruption of services like sewer and water lines, loss of life, and causes instability in both economic and social components of the affected nation (Webcache 2).